1. Field of Invention
The present invention relates to smart structure egress channels, particularly to a channel providing a central location for multiple sensors embedded therein to come together for both signal processing and signal egress from the structure.
2. Description of Prior Art
With the advent of microchip technology and advanced communications, it is now advantageous to use remote sensors to monitor and transmit the physical status of certain structures. This information can be displayed and utilized to alert humans of impending structural failure. These so-called `smart structures` can communicate a building's environmental status either floor by floor or room by room. Aircraft smart structures can monitor and warn one of a variety of conditions which affect flight capability and crew safety.
It is advantageous to have the integral sensors within smart structures transmit their output through a central location or junction. A central junction where output signals can be processed, enables the transmission of data from a single exit point in the structure. Also a central junction provides a maintenance port for servicing the sensors.
Current aircraft structures offer a unique challenge to the gathering of sensor information and their ultimate use. The multi-laminate design of modern aircraft necessitates an embedded junction device which is compact, able to survive repeated strains, lightweight and which conforms to the configuration of the aircraft's structure. However, the junction site is desired to accommodate a variety of sensor inputs and a single output. Additionally, easy access is important so as to repair and replace the sensor and update the sensors as time and technology dictate. Currently, the installation and use of sensor inputs are complex and expensive. Typically each sensor cable is terminated at the exterior of the composite structure. Each sensor cable is protected by a collar. The tremendous danger involved is that at the exterior, collar and sensor egress point, the sensor cable will accidently shear off during the manufacturing process. To guard the sensor cable against this occurrence several layers are placed over the sensor, collar, and exterior interface. With the presence of multiple sensors, the labor and additional materials may substantially increase the cost of manufacturing a composite structure.
Attempts have been made to use existing electrical junction boxes as sensor junction sites, but have met with little success. See Rita Robison, `Smart Structures`, Civil Engineering, November 1992, p. 66-68. In the Robison article, an ordinary electrical conduit box was used to house the sensor outputs.
Such electrical conduit or junction boxes are well known in the prior art. For example U.S. Pat. No. 5,216,203 ('203) discloses a typical design. Such conduit junction boxes are unable to accommodate a sufficient number of sensor inputs. That is, such electrical junction boxes cannot accommodate more that about four electrical inputs. Additionally, the junction boxes are incompatibly heavy and bulky for the size and weight restrictions in modern aircraft. Furthermore, the inside of a typical electrical junction box is inaccessible after project completion. Detailed maintenance would be troublesome, if at all possible, to undertake. The prior art junction boxes are not able to sustain the placement of a significant load. The prior art junction boxes are placed in locations which were not primary load bearing locations. Besides being incapable of handling a significant load, the prior art junction boxes are incapable surviving the temperatures necessary in the creation of current composite structures. For instance a typical plastic junction box can only survive to temperatures of 140.degree. F. However, the processing of many composite structures occurs at temperatures up to 350.degree. F. Another material which the prior art junction box uses is aluminum. However the combination of a aluminum junction box and carbon-based fiber used in a typical composite structure will create a galvanic cell and corrode an aluminum junction box.
Other electrical housing boxes suffer similar drawbacks to those discussed above. Housing units for transformers (see U.S. Pat. No. 5,177,325) electromechanical equipment (see U.S. Pat. No. 5,029,270) and portable power distribution equipment (see U.S. Pat. No. 5,202,538) are all unsuitable in size, weight and design. They lack sufficient interior detail and properly sized holes to accommodate sensor input.
A design which would eliminate these deficiencies would be a welcomed advancement in the art.